Through-flow aspirator muffler

ABSTRACT

Muffler for silencing output of aspirator. End caps support spaced concentric tubes of porous acoustical material, inner tube lined and outer tube covered with foraminous metal. Connections through caps to bore of inner tube permit through-flow output of aspirator and material carried thereby.

1 1 Sept. 5, 1972 [$4] THROUGH-FLOW ASPIRATOR MUFFLER [72] Inventor: Stephen J. Gibel, 5846 Edgerton Road, North Royalton, Ohio 44133 22 Filed: Aug. 26,1971

21 Appl. No.: 175,174

[521 US. Cl. ..18l/SS, 181/60, 181/61, 181/50 [51] Int. Cl. ..F0ln l/10, F01n 7/18 [58] Field of Search ..181/35 A, 61, 48, 59, 54,60, 181/55, 56, 42, 50

[56] References Cited UNITED STATES PATENTS R22,283 3/1943 Boume ..181/55 1,103,769 7/1914 Hintz ..l81/59 2,543,461 2/1951 Latulippe ..1s1/4s 3,175,640 3/1965 Matsui ..18 1/55 FOREIGN PATENTS OR APPLICATIONS 379,563 9/1932 Great Britain ..1s1/35 A 406,442 3/1934 Great Britain ..1s1/35 A 841,828 7/1960 Great Britain 181/59 Primary Examiner-Robert S. Ward, Jr. Attorney-Fly, Golrick & Flynn [57] ABSTRACT Muffler for silencing output of aspirator. End caps support spaced concentric tubes of porous acoustical material, inner tube lined and outer tube covered with foraminous metal. Connections through caps to bore of inner tube permit through-flow output of aspirator and material carried thereby.

5 Claims, 2 Drawing Figures THROUGH-FLOW ASPIRATOR MUFFLER This invention relates to means for silencing the blasts of air-aspirators, and more particularly, to means for permitting the through flow of the output of such aspirator-s, including the material carried thereby, such as textile filaments and yarns.

In textile mills, any broken filament or yarn end must be retrieved from among the many other unbroken ends being spun, woven, or knitted, and then re-connected and/or placed at its proper position in the textile machine. This is necessary to avoid further damage to the yarns or fabric as well as to prevent the possible consequent damage to the textile machinery if broken ends were not retrieved but allowed to accumulate. To avoicl the difficulty and delay of retrieving a broken end by hand, the industry has long employed hand-held air aspirators. Such an aspirator comprises an open-ended nozzle tube into the inner periphery of which high-pressure air can be injected by operation of a valve in the air line to the nozzle. Injection of the air creates a powerful vacuum in the entrance to the nozzle; when suction inlet to the aspirator is placed near the broken end, it will be sucked into the nozzle and thereby be retrieved.

Heretofore a long-standing and seemingly inherent and inescapable problem in the use of such as aspirator has been the earsplitting blast it produces when operated. Any conventional muffler having the capacity for the large output of air of such an aspirator would be too bulky and unwieldy and, further, would cause long broken ends of yarn or filament to tangle in it, whereas a purpose of the straight open-ended nozzle of the aspirator is to blow the broken end out so that it can be retrieved without tangling. Likewise, any prolonged back pressure on the aspirator nozzle created by baffles, screens, or porous elements of conventional nozzles, or even the initial back-pressure created by the inertia of the static air in a conventional muffler as it is hit by the sudden output blast of the aspirator nozzle, will impair the efficient operation of the aspirator.

It is an object of this invention to provide a muffler which substantially reduces the noise of the output blast of such an aspirator; it can be light and compact and attached to the output of the aspirator without impeding the manipulation of the aspirator. A further advantage of a muffler made according to this invention is that it allows the broken end to be blown through it without tangling.

Other objects and advantages of this invention will be apparent from the following description, claims, and drawings, in which:

FIG. 1 is an end view of a muffler made according to this invention.

FIG. 2 is a longitudinal section taken along the line 22 of FIG. 1.

Referring to the drawings, the muffler comprises a pair of opposed end caps and 10'. The cap 10 has a central internally threaded boss 11 and is provided with a circumferential axially extending flange 12 which provides a seat for one end of the outer tubular body 20. The boss 11 carries a nipple 13. The nipple 13 extends into the cap 10 beyond the inner surface of the dome-shaped wall 14 between the boss 11 and circumferential flange 12. The inward extension of the nipple 13 centers and supports one end of the inner tubular body 30. The nipple 13 extends outwardly of the boss l 1 so that the muffler may be connected to the output end of an aspirator nozzle by the nut faces on the boss 11. The cap 10' has a corresponding boss 11', flange 12', and nipple 13' similarly located and extending with respect to its wall 14. Both caps 10 and 10 have a pair of small internal bosses 16 and 16', respectively, one pair being drilled and the other tapped to receive the tie bolts 17 by which the bodies 20 and 30 are held between the end caps. As shown, the muffler is "double-ended;" since the muffler is symmetrical between the nipples 13 and 13', its overall length and weight may be slightly reduced by cutting one of the bosses 1 1 or 11' to a length which is no more than required to support a short nipple extending only into the interior of the muffler to support and center an end of the tubular inner body 30. The so-shortened end will then become the discharge end of the muffler.

The outer tubular body 20 is comprised of an inner layer of sound-absorbing acoustical material which, in this illustrated embodiment, is a tube of highly porous, loosely felted cellulosic fibers bonded together with a sufficient amount of resinous binder to give the material sufficient mechanical strength to be self-supporting. To protect the relatively soft tubular wall 21 from abrasion and wear during handling and use and also to carry at least some of the compressive load imposed by the tie-bolts 17, the wall 21 is covered with an outer shell of foraminous metal 22, which may be open-mesh wire screen but, in the preferred embodiment illustrated, it is of perforated metal in which the area of the perforated holes is preferably 50 to percent of the area of the outer surface of the body exposed between the flanges 12 and 12'.

The inner tubular body 30 is comprised of a tube 31 of acoustical material, preferably the same as the material 21 of the body 20. The tube 31 is lined with a foraminous metal tube 32, also preferably similar to the outer metal tube 22 of the body 20. The liner 32 may also carry some of the structural load of the tie bolts 17, but its primary function is to protect the acoustical material 31 from destructive effect of the sudden blasts of air entering the muffler from the output of the aspirator (the impact of which might otherwise burst the tube 31) and to distribute the kinetic energy of the blast along the length of the inner body 30, from which it is disseminated into the chamber 25 between the tubes 21 and 31.

It is to be noted that the wall thickness of the tube 31 is preferably less (in the order of 40-60 percent) than the wall thickness of the tube 21. The impedance of dispersion of the kinetic noise-producing energy of air through the tortuous passages of acoustical material such as that of the tubes 31 and 21 appears to be a function of its exposed area and thickness and thus, with its small exposed area, the thickness of the wall 31 is less in order to minimize impedance to the dispersion of the moving air in the tube 31 into the annular chamber 25, where excess sound energy as might reverberate within the chamber 25 is absorbed by the porous opposed surfaces of the tubes 31 and 21 and the balance is dispersed by the gentle emission of the air through the wall 21. The lengths of the tubes 21 and 31 and the inner and outer diameter of the tube 21 is a matter of compromise to achieve the desired result of the muffler. If the length of the tubes with respect to the diameter of the tube 32 is in the order of 4:1 or less,'

the noise may not be sufficiently reduced from that of an unmuffled aspirator to render the mufi'ler generally acceptable. If the ratio is in the order of 12-1521, the noise of the blast will usually be reduced to less than that of the ambient atmosphere. This would be a greater noise reduction than necessary and the muffler would not only become an unwieldy attachment but so much of the air ejected by the aspirator would be dispersed through the bodies 30 and and its kinetic energy could be so reduced as to be insufficient to blow even light yarns out of the outlet of the muffler without tangling (such ejection from the outlet of the muffler signals the operator that the broken end has been picked up and the aspirator may be shut off). A tube length with respect to the inner diameter of the inner body of the order illustrated, i.e., 7-8: l has proved to efi'ect significant and substantial noise reduction, allowing requisite through-flow of the output air of the aspirator and filament and yarn carried by it. Due to the open discharge end of the muffler, no significant static pressure builds up as back-pressure in the muffler during operation and the mass of air within the tube 32 before operation is insufficient to create a significant initial back-pressure to interfere with the aspirator when it is initially actuated.

This invention is not to be limited to the specific embodiment disclosed in the drawings and described, but may be further modified by those skilled in the art without departing from the scope defined in the appended claims.

What is claimed is:

l. A through-flow mufiler for air-aspirator comprising a pair of concentric inner and outer tubes each comprising a wall of porous sound-absorbing acoustical material, a pair of end caps supporting said tubes in their concentric relationship and enclosing an annular chamber between them, said caps having aligned openings providing a straight and substantially unrestricted conduit through said inner tube, and means to connect one of said end caps at its central opening to the output of an aspirator.

2. A muffler as defined in claim 1 in which said inner tube is provided a liner of relatively rigid and hard foraminous material to distribute the force of a blast of air from an aspirator along the length of said inner tube and permit the dissemination of said air and its kinetic energy through the porous acoustical material of said tube into said annular chamber, the area of the openings in said foraminous material with respect to its entire area ranging from 30 to percent.

3. A muffler as defined in claim 2 in which the ratio of the length of said tube with respect to the inner diameter of the inner tube ranges between 4:1 and 12-511.

4. A muffler as defined in claim 3 in which the wall thickness of the acoustical material in the inner tube is less than the wall thickness of the acoustical material in the outer tube.

5. A muffler as defined in claim 4 in which the outer surface of the acoustical material in said outer tube is covered with a foraminous material similar to the lining of said inner tube.

l I! t III 

1. A through-flow muffler for air-aspirator comprising a pair of concentric inner and outer tubes each comprising a wall of porous sound-absorbing acoustical material, a pair of end caps supporting said tubes in their concentric relationship and enclosing an annular chamber between them, said caps having aligned openings providing a straight and substantially unrestricted conduit through said inner tube, and means to connect one of said end caps at its central opening to the output of an aspirator.
 2. A muffler as defined in claim 1 in which said inner tube is provided a liner of relatively rigid and hard foraminous material to distribute the force of a blast of air from an aspirator along the length of said inner tube and permit the dissemination of said air and its kinetic energy through the porous acoustical material of said tube into said annular chamber, the area of the openings in said foraminous material with respect to its entire area ranging from 30 to 70 percent.
 3. A muffler as defined in claim 2 in which the ratio of the length of said tube with respect to the inner diameter of the inner tube ranges between 4:1 and 12-15:1.
 4. A muffler as defined in claim 3 in which the wall thickness of the acoustical material in the inner tube is less than the wall thickness of the acoustical material in the outer tube.
 5. A muffler as defined in claim 4 in which the outer surface of the acoustical material in said outer tube is covered with a foraminous material similar to the lining of said inner tube. 